Moving Charges and Magnetism — Physics STD 12 Science — Question

An electron having charge ‘e’ and mass ‘m’ is moving in a uniform electric field E. Its acceleration will be

(a)

(b)

(c)

(d)

Find the false statement.

The frequency and work function of an incident photon are n and . If n_­0 is the threshold frequency then necessary condition for the emission of photo electron is

(a)

(b) v =

(c)

(d) None of these

Mark out the correct options.

The energy contained in a small volume through which an electromagnetic wave is passing oscillates with:

Electric potential is given by T, hen electric force acting on 2C  point charge placed on origin will be

(a) 2N

(b) 6N

(c) 8N

(d) 20 N

The temperature coefficient of resistance of a conductor is

(a) Positive always

(b) Negative always

(c) Zero

(d) Infinite

Ten grams of ⁵⁷Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly:

1. 10g
2. 5g
3. 2.5g
4. 1.25g

A parallel plate air capacitor is charged and then isolated. When a dielectric material is inserted between the plates of the capacitor, then which of the following does not change

(a) Electric field between the plates	(b) Potential difference across the plates
(c) Charge on the plates	(d) Energy stored in the capacitor

The alternating voltage induced in the secondary coil of a transformer is mainly due to

(a) A varying electric field	(b) A varying magnetic field
(c) The vibrations of the primary coil	(d) The iron core of the transformer